By the serum is meant an aqueous solution byproduced upon coagulation and removal of a rubber component from a natural rubber latex. Serums have in most instances been disposed as wastes with the result that countries and territories of rubber tree cultivation are involved in environmental pollution problems.
However, such serums are thought to provide a good source of bacterial nutrition and hence a vast biomass as they are composed of proteins, organic acids, saccharides and derivatives thereof. Limited application of the serum has been found as a rubber additive as disclosed in Japanese Patent Publication No. 63-161002.
Bacteria have been allowed to grow, in the micrological industry, with the supply of various nutrition elements typified by amino acids, vitamines, minerals and the like and taken alone or in combination. In general, naturally occuring nutritions such as organic nitrogen are used to attain multinutrient cultures for bacteria. These nutrition elements are selected usually from a great number of materials including yeast extracts, polypeptones, meat extracts, defatted soybeans, defatted soybean hydrolyzates (HVP), corn steep liquors (CSL), cotton seed meals, peanut meals, pharmamedia, distillers solubles, livestock bloods, butchery wastes, casein hydrolyzates and the like.
Nutrition elements for use in culture media in commercial fermentation are required to be low in cost, abundant in supply without seasonal irregularities, stable in quality and effective for a wide variety of bacteria. Those meeting such requirements are limited only to HVP, CSL and yeast extract among the above listed nutrition elements. Because of their source of supply from byproducts in the food industry, however, HVP and CSL have posed an extreme shortage and a high price as a result of the changeover of processing methods in that industry. Yeast extract literally costs too high to warrant commercial acceptance.